Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> writes: >> > IOW, it is ftrace save regs/restore regs code issue. I need to check how the >> > function_graph implements it. >> >> gpr2-gpr14 are always saved in ftrace_caller/ftrace_regs_caller(), >> regardless of the FTRACE_WITH_REGS flags. The only difference is that >> without the FTRACE_WITH_REGS flag the program status word (psw) is not >> saved because collecting that is a rather expensive operation. > > Thanks for checking that! So s390 will recover those saved registers > even if FTRACE_WITH_REGS flag is not set? (I wonder what is the requirement > of the ftrace_regs when returning from ftrace_call() without > FTRACE_WITH_REGS?) Yes, it will recover these in all cases. >> >> I used the following commands to test rethook (is that the correct >> testcase?) >> >> #!/bin/bash >> cd /sys/kernel/tracing >> >> echo 'r:icmp_rcv icmp_rcv' >kprobe_events >> echo 1 >events/kprobes/icmp_rcv/enable >> ping -c 1 127.0.0.1 >> cat trace > > No, the kprobe will path pt_regs to rethook. > Cna you run > > echo "f:icmp_rcv%return icmp_rcv" >> dynamic_events Ah, ok. Seems to work as well: ping-481 [001] ..s2. 53.918480: icmp_rcv: (ip_protocol_deliver_rcu+0x42/0x218 <- icmp_rcv) ping-481 [001] ..s2. 53.918491: icmp_rcv: (ip_protocol_deliver_rcu+0x42/0x218 <- icmp_rcv)
